Invalid SIM msg (which works in other phones)

[Guest RockStar72]

I bought an unlocked AT&T branded SGH-i617 from Canadian web store last year. I upgraded it successfully to WM 6.1 and then brought it back to the UK with me and signed up with T-Mobile (I just like their Flext plans!).

It worked fine for about 2 months then one day decided to show "invalid SIM" and wouldn't let me do anything with the phone - I couldn't get past that message. The T-Mobile SIM would work fine in other phones (I've since purchased a god awful KU-990 but hey, at least it makes calls and txts) and I've put an old AT&T SIM in the phone for testing.

What I have tried from reading posts about this error message on other phones is this:

1. Take the sim out, use a pencil eraser (rubber if you're in the UK :excl: ) to clean the sim contacts and the phone contacts

2. Pressed the old power on set of keys to get to the low level software to format the phone (Home, down and power on possibly? The same one used in the WM6.1 upgrade to reboot the thing)

3. Tried with and without SIM cards in

Now what it's doing when switched on is to show the animated swishing 3G bars, shows the WM bootup screen, then it switches itself off after a few minutes (with the animated "Goodbye" screen)

Oddly, if I plug the phone into a usb port on my compy (Ubuntu Linux) the compy's network manager connects to "auto eth2" automatically. It doesn't do anything of course, but it "feels" like the phone's not entire dead.

Is there anything I can do to reincarnate it? I can run windows on other compies as I know there's so many issues with running this phone through ubuntu, if that helps :excl:

I really liked this phone and would love to have it working again

Thanks